1. Field of the Invention
This invention relates to an overhead door closer with slide arm assembly, having a piston being guided in a housing and leaning against a closing spring, having a toothed pinion being eccentrically, rotatably supported at the housing, and meshing with a toothed rack of the piston, which pinion presents a circular rolling curve, the central point thereof being offset, in relation to the rotary axis of the pinion in the closing position, into the direction towards the toothed rack, and in relation to the rotary axis in the opening position, into the opposite direction.
2. Description of the Related Art
The above described overhead door closers with slide arm assembly, also known as rack and pinion door closers, with regard to traditional door closers, advantageously do not present an arm assembly protruding uncovered into the room, but they simply present an actuation arm sitting close and flat at the door frame or at the door leaf. They do, however, bear the disadvantage that the actuation arm, sitting close and flat at the door frame or at the door leaf, leads to an unfavourable course of forces at the door, in relation with conventional, symmetric rack and pinion mechanics. It is therefore an object to conceive an optimal rack and pinion drive, with the intention to achieve, during the opening procedure and closing procedure of the door, an operation of the pinion, as low in friction and smooth as possible, at the associated toothed rack and therefore of the piston inside the piston housing.
Centrically or eccentrically supported pinions are used in known door closers.
A door closer species, described at the beginning, having an eccentrically supported pinion is known from EP 0 856 628 A1, wherein the toothing of the toothed rack forms a linearly extending pitch line of engagement having an angle comprised between 4.5° and 7.2° with regard to the moving direction of the piston. The selection of an angle depends on the size of the door closer, respectively on the strength of the closing spring. Because of the eccentric support of the pinion and of the linear course of the toothed rack, an optimal, especially low friction and smooth progress of the pinion's teeth at the toothed rack is not guaranteed; there are spreads in the course of the momentums' curves.
A comparable solution applying a linearly extending toothed rack with an angle is described in U.S. Pat. No. 633,682.
Furthermore DE 36 45 313 C2 and DE 36 45 314 C2 reveal an eccentrically supported pinion where a rolling curve, arranged at the pinion, is used, having various lever arms in relation to the rotary axis. Accordingly, the rolling curve of the associated toothed rack extends in an arcuate form.
In a door closer known from DE 82 17 72 C2 respectively from the French Patent Application 96 69 45, the closer shaft is connected at an eccentrically supported elliptical toothed wheel meshing with an inclined toothed rack on the piston side. Up to a certain degree, a transmission, adapted to a desired course of the momentum, is achieved by means of the elliptical gear due to the differently long lever arms of the elliptical toothed wheel.
The pneumatic door closer according to U.S. Pat. No. 1,359,144 presents a circular eccentrically supported pinion which meshes with an uneven toothed rack at the piston. The circular pinion is provided with a regular toothing on a circular rolling curve, whereby varying lever arms come into effect due to the eccentrical support.
Various piston drive embodiments in door closers are described in DE 36 38 353 A1, in EP 0 207 251 A2, in DE 94 12 64 and in U.S. Pat. No. 2,933,755, whereby in relation with eccentrically or centrically supported pinions—if necessary with insertion of a transmitting gear drive—a direct charge of the closing spring is exerted by means of a crank drive.
Centrically supported pinions are known from EP 0 056 256 A2 as well as from EP 0 350 568 A2. EP 0 056 256 A2 deals with a door closer, the pistons thereof presenting two symmetrically, diametrically opposite toothed racks, whereby a centrically supported pinion engages, in the closing position, with shortened teeth, in both toothed racks of the piston.
The door closer according to EP 0 350 568 A2 presents a centrically supported pinion, which presents teeth extending at the circumference, with progressively increasing depths of teeth, which teeth engage between the rods of a correspondingly curve-shaped extending toothed rack.
A substantially centrically supported pinion of a drive for a door or for a window is disclosed in DE 44 44 131 A1 and DE 44 44 133 B1, wherein the pinion itself presents a toothing over up to approximately half the circumference thereof, the teeth thereof being disposed at lever arms varying in length and progressing on a correspondingly curved rolling curve of a toothed rack.